Magnetic soft micromachines made of linked microactuator networks

TLDR

Soft untethered micromachines smaller than 100 µm can perform diverse programmed shape transformations and functions for biomedical and organ‑on‑a‑chip applications, but their fabrication has been limited by poor control over microactuator programmability. The authors aim to overcome this limitation by selectively linking Janus microparticle‑based magnetic microactuators using two‑photon polymerization to create 3D‑printed soft or rigid polymer links. They position each microactuator by surface rolling and magnetic‑field torques, then 3D‑print soft or rigid links to connect temporarily fixed microactuators into networks. The resulting linked 2D microactuator networks demonstrate programmed 2D and 3D shape transformations, and limbless or limbed micromachine prototypes exhibit various robotic gaits for surface locomotion, indicating that the fabrication strategy enables soft micromachine designs at cellular scales.

Abstract

Soft untethered micromachines with overall sizes less than 100 μm enable diverse programmed shape transformations and functions for future biomedical and organ-on-a-chip applications. However, fabrication of such machines has been hampered by the lack of control of microactuator's programmability. To address such challenge, we use two-photon polymerization to selectively link Janus microparticle-based magnetic microactuators by three-dimensional (3D) printing of soft or rigid polymer microstructures or links. Sequentially, we position each microactuator at a desired location by surface rolling and rotation to a desired position and orientation by applying magnetic field-based torques, and then 3D printing soft or rigid links to connect with other temporarily fixed microactuators. The linked 2D microactuator networks exhibit programmed 2D and 3D shape transformations, and untethered limbless and limbed micromachine prototypes exhibit various robotic gaits for surface locomotion. The fabrication strategy presented here can enable soft micromachine designs and applications at the cellular scales.